Synthetic decking products such as Fiberon, TimberTech, and Azek have come a long way in recent years. In general, though, I don''ve begun building decks using cold-rolled light-gauge (LG) galvanized steel joists that allow me to offer customers a frame that will last as long as the decking I put on it.
Getting the Permit
Before jumping on the steel bandwagon, call your local building department and find out its requirements for steel-framed decks. The IRC covers steel joists extensively, and it''s stamp for steel-framed decks. That sets me back $400 to $600 per project, but having the stamp is reassuring for me and helps customers accept what in their mind is an unconventional system. If your building department also requires an engineer, look for one with commercial construction experience - he or she will be familiar with steel framing and should understand the concept of using it for a deck.One objection that crops up with steel joists is their shiny look - it''s 2-by dimension). All play a role in determining the capacity of the joist; the size joist you must use will depend on the loading requirements in your local code. Steel suppliers such as Cemco (cemcosteel.com) provide span charts to aid in specifying joist size.
Typically, LG steel comes as joists (or studs) and track. If you''re probably familiar with the difference. Track is sized so that the studs or joists fit inside it. For walls, track is used for the plates; for deck framing, it''t stock steel framing members. Around here, drywall supply houses handle LG steel studs and track. Drywall suppliers might not have the sizes you need in stock, but they''t waste 1 foot to 3 feet of material for each joist on a 13-foot deck. Ordering to length can also limit the number of cuts required for a project and save some time. Plus whatever scrap is generated on site is completely recyclable - in fact, you may be able to get a few bucks for it at a scrap yard.
Steel joists have other advantages over wood. They weigh roughly half what an equivalent wood joist does, making them a lot easier to maneuver. And you don''s usually from mishandling by the supplier. Pieces over 20 feet long should be handled by two people to prevent bending and creasing. Hand unloading from the delivery truck is also advised if a fork truck is not provided.
Putting It Together
Steel framing tends to take more time to assemble than wood framing, primarily since instead of using pneumatic nailers, you use drills and impact drivers. It takes quite a bit longer to drive eight #10-16 by 3/4-inch self-tapping screws into an LS70 than to nail up a joist and hanger with for 1 last update 2020/08/06 a nail gun. Clamping the LS clips in place with Vise-Grip C-clamps makes the job go a little quicker (Figure 3).Steel framing tends to take more time to assemble than wood framing, primarily since instead of using pneumatic nailers, you use drills and impact drivers. It takes quite a bit longer to drive eight #10-16 by 3/4-inch self-tapping screws into an LS70 than to nail up a joist and hanger with a nail gun. Clamping the LS clips in place with Vise-Grip C-clamps makes the job go a little quicker (Figure 3).
I cut the steel with a standard circular saw and a special blade designed for cutting LG steel. Freud Diablo blades (800/334-4107, freudtools.com) perform well and cost roughly $40. They last one to two projects, depending on the gauge of the steel and the quantity of cuts. Cheaper blades are available, but I''t use abrasive blades, as they heat up the galvanization, which affects its quality and durability. While the steel blades aren''t hurt to hit the ends with some zinc paint.
Full protection - particularly eye and face protection - when cutting is a requirement . I use a flip-down face mask (Figure 4). Long sleeves, pants, and gloves minimize cuts and small burns from the hot metal. Also, cutting steel sends small bits of metal some distance. Think about this when setting up a cut station - small bits of metal that land on your decking pile can cause stains.
Start installation by attaching a ledger of track pretty much as you would a wood ledger (Figure 5). Flash the ledger just as you would a wood ledger, using bituminous membrane, vinyl, or galvanized steel flashing to avoid any corrosion problems. I fasten the ledger to the house with two 1/2-inch-by-21/2-inch lags every 16 inches.
The easiest way to prep the ledger is to lay out for the joists first, then lay out for the lags, using a permanent marker on the steel. Predrilling the holes for the lags with a step drill (Figure 6) is much faster than using a 1/2-inch twist bit. I usually start with a 1/8-inch pilot bit, opening the hole to 1/2 inch with the step bit. Touch up the holes and cuts with zinc paint. While I''s not a big issue in Colorado with our dry climate.
Mini Catapult DIYhow to Mini Catapult DIY for Next, I build and install the beam. The beam is built up from joist and track material (Figure 7), either as a single beam or a double beam, depending on the spans and loads. The single is one piece of joist and one piece of track screwed together every 12 inches; the double beam is two pieces of joist and two pieces of track, also screwed together on 12-inch centers. I cover the top of the beam with adhesive membrane to keep out water (Figure 8). Screws through the joist flanges will secure them to the beam.
There are several instances where blocking is required. If you''ll need blocking on top of the beam at every other joist to prevent the joists from rolling (Figure 9). Cut blocking from joist material and fasten it with LS brackets. Also, midspan blocking is a good idea on spans greater than 10 feet. To make installing it easier, I usually order some material that''t fit well. Instead, my engineer approves the use of a piece of 4 1/4-inch track secured to the pier with four 1/4-inch concrete anchors as a post base (Figure 12). The post sits inside this track, and screws through the sides of the track complete the connection. For post caps, Simpson''s a flush beam). Predrill and screw them together.
For rail posts, I usually use redwood (it''s not likely to have a corrosive reaction with the galvanized steel). I bolt the posts to the frame in a similar manner as to a wood frame, using two 1/2-inch-by- 6-inch bolts (Figure 13).
On most of my decks, I build the stairs with traditional pressure-treated-wood stringers (be sure to fully isolate the PT from the galvanized steel), hung with Simpson bulk roll strapping. Steel stringers can be built, but they are much more complicated and expensive (Figure 14).
The C-shape of the joists allows for screws to be driven through the flange and into the bottom of the decking for a fastener-free surface with all the benefits of face screwing (Figure 15). Predrill the joists from above before placing the decking and fasten from below with #8 by 1-inch galvanized screws.
Robert Shaw owns Colorado Deck and Framing in Colorado Springs.
For More Information
Steel Stud Manufacturers Association
Engineering information, list of manufacturers
Supplier, span tables
Mini Catapult DIYhow to Mini Catapult DIY for cemcosteel.com
The Steel Network
Supplier, free steel-deck software
About the AuthorRobert Shaw
Mini Catapult DIYhow to Mini Catapult DIY for Robert Shaw the 1 last update 2020/08/06 owns Colorado Deck and Framing, in Colorado Springs, Colo. Robert Shaw owns Colorado Deck and Framing, in Colorado Springs, Colo.